Fruit-Crops.com

was developed as an online aid to the class 'Introduction to Fruit Crops' (HORT 3020) at UGA. The material is from the book that I wrote for HORT 3020 ('Introduction to Fruit Crops'), a book still used in the class today, and it is reliable as a reference for any internet-based or traditional college class.

Here you will find fruit horticulture and agriculture tips for an online hort degree program for distance learning but you don't need to be a horticulture major or even working on a bachelor's or Master's degree to use the site.

Over the years I have enjoyed hearing from students, teachers, professors, government officials, farmers, crop industry experts and others from all over the world about fruit crops. If you have a question or comment please do not hesitate to contact me.

Also, please feel free to cite this information without permission for non-commercial purposes.

Thanks for visiting,
Mark

About Mark:

On August 1, 2012, Mark Rieger took office as dean of the University of Delaware's College of Agriculture and Natural Resources.

Rieger served as associate dean and professor in the University of Florida's College of Agricultural and Life Sciences since 2006 and was interim dean in 2010-11. As associate dean, Rieger had major responsibilities in graduate programs, distance education, statewide degree completion programs, the honors program and international education.

Prior to joining the University of Florida faculty, he was a professor in the University of Georgia's Department of Horticulture from 1999-2006. He joined the University of Georgia faculty as an assistant professor in 1987 and was promoted to associate professor in 1993 and professor in 1999.

Rieger received a bachelor's degree in horticulture in 1982 from the Pennsylvania State University, a master's degree in horticulture in 1984 from the University of Georgia and a doctorate in horticultural sciences in 1987 from the University of Florida.

Glossary – Introduction to Fruit Crops

Accessory – a term given mostly to aggregate fruits in which the conspicuous and often edible portion is non-ovarian in origin. Example – strawberry, where the receptacle is the fleshy, edible portion, and the true fruit an achene.

Achene – a dry, indehiscent, one- or two-seeded fruit, with generally thin pericarp loosely attached to the seed(s). Fruit is generally small, and comes from a unicarpellate ovary. Example – sunflower, where the thin, black pericarp (shell) surrounds the single seed.

Aggregate – a fruit derived from two or more ovaries contained within a single flower; may contain non-ovarian tissue. Example – blackberry, where each fruit is an aggregate of drupelets attached to a common receptacle. Raspberry is also an aggregate of drupelets but does not contain receptacle tissue.

Albedo – The mesocarp of a citrus fruit; the white, spongy tissue lying between the colored peel and the juice sacs.

Alternate bearing (syns biennial bearing, irregular bearing) – high production of fruit one year followed by low production the next. Common in nut trees.

Androecium – the stamens of a flower, collectively.

Anther – The swollen, apical, pollen-bearing section of the stamen.

Anthesis – Time of flower expansion when pollination takes place.

Anthocyanin – a class of water-soluble pigments responsible for the red, purple, and blue coloration of flowers and fruits.

Apomixis, apomictic seed (Syn agamospermy) – reproduction of a plant through a seed wherein the embryo has arisen clonally from nucellar or integument tissue, and is genetically identical to the parent plant.

Bench Graftage – Grafting technique where the union is made at a propagation bench instead of a potted or soil-rooted plant; involves storage and callusing of rootstock and scion wood during the winter, and specialized cuts made with special tools or saws. Common with grape.

Bearing habit – The position of the flower buds, with respect to the type and age of wood. For example, “spur bearing” trees produce flowers (thus fruits) on short, long-lived, lateral branches called spurs.

Berry – a fleshy, indehiscent fruit with more-or-homogeneous texture throughout, derived from a single, superior ovary. One- to many-seeded. Example – grape. Term often misused. An epigynous berry is same derived from an inferior ovary (like blueberry).

Bisexual (syns hermaphroditic, perfect) – having both sexes present.

Bloom – epicuticular wax found on the surface of a plant organ, particularly fruits. Also, used as synonym for flower or anthesis (which see).

Bract – A modified leaf structure that subtends a flower or inflorescence.

Brambles – a group of fruit crops in the genus Rubus. Includes blackberries, raspberries, and hybrids thereof.

Budding – Means of vegetative propagation where the scion is reduced to a single bud, usually axillary, which is inserted into a rootstock. Main types used for fruit trees are T-budding and chip budding.

Bur (also Burr) – A spiny appendage; the involucre of a chestnut fruit.

Burrknot – concentration of preformed root initials on a stem or the trunk; can cause partial girdling and stunting of the tree.

Bushel – a unit of measurement of fruit yield, equal to about 50 lbs. Generally, wooden baskets or boxes are used, with a volume of about 1/28th of a cubic meter.

Carpel – the megasporophyll, or structure enclosing the ovules (seeds). If a simple ovary, then the carpel and ovary are the same structure. If a compound ovary, then it is comprised of 2 or more carpels.

Catfacing – injury to fruit, generally from insects, resulting in severe distortion of fruit shape. Occurs when an area of the surface of a young fruit is injured, killing the tissue, but surrounding healthy tissue continues to grow and develop.

Catkin – a slender, flexible, pendulous spike.

Cauliflory (cauliflorous) – a term applied to plants that bear flowers and fruit on main stems or trunks, such as cacao, jackfruit, and jaboticaba.

Central leader – A tree training system where a main central bole (the “leader”) extends from the trunk of the tree. At intervals along the central leader, tiers of fruiting scaffolds are trained, with the lowest tier extending the furthest, and the upper tier extending only a few feet, giving an overall shape like a Christmas tree.

Chasmogamous – Flowers that must open before pollination; opposite of cleistogamous. Often seen in cross-pollinating species.

Chilling requirement – The time of exposure to cool, nonfreezing temperatures during winter required to allow normal budbreak and development the following spring. Measured in hours at or below 45°F from approximately leaf drop in fall throughout the winter.

Circumscissile capsule (syn Pyxis) – a dry, dehiscent, one- to many-seeded fruit from a single, compound ovary, opening at the equator, with the top separating like a lid.

Compound – an organ composed of multiple parts, as a compound leaf where the blade is composed of leaflets, or a compound ovary divided into 2 or more carpels.

Compound spadix – an inflorescence composed of multiple branches with a more or less common point of attachment, each of which is a spadix. The inflorescence type of many palms.

Controlled Atmosphere storage – subjecting fruit to low oxygen and high carbon dioxide during cold storage to extend postharvest life.

Cordon – a permanent, horizontally trained limb; most commonly used in grapes to denote the major scaffolds.

Corm – a shortened, vertically oriented, solid underground stem.

Corolla – the petals, collectively.

Corymb – an indeterminate inflorescence where flowers are born in a plane or slight arc. The pedicels of lowermost flowers are elongated and those of uppermost flowers shortened so that all flowers are displayed at about the same height (expear). Similar in shape to an umbel but with pedicels arising from different points on the main axis.

Cross-compatible – Pollen of one plant is capable of fertilizing ovules of another, genetically distinct plant.

Cross-pollination – pollen transfer between the anther and stigma of two genetically distinct plants.

Cross-sterile – inability of a plant to produce fruit with viable seed when cross-pollinated by another genetically distinct plant; does not preclude parthenocarpic fruit set and development.

Cross-unfruitful – a genetically distinct plant is used as a pollinizer for another plant and the latter fails to produce a commercial crop.

Delayed dormant spray – a pesticide application applied to trees when buds have begun to swell, but new tissues are not yet fully exposed.

Delayed incompatibility – a situation where a rootstock and scion appear to be compatible and grow vigorously for several years, after which time the tree declines and may eventually break cleanly at the graft union.

Determinate – term applied to inflorescences having the top-most or central flower appearing and maturing first in the blooming sequence.

Dormant oil – an important spray material for most fruit trees; emulsifiable oil is mixed with water and applied to trees before buds swell, killing many overwintering pests.

Dormant pruning – pruning during the dormant season.

Double budding – placing a thin sheath of wood between the rootstock and scion bud to serve as a compatibility bridge. Results in a tree with an extremely short interstem.

Double fertilization – In angiosperms, the union of one generative nucleus from a pollen grain with the egg, yielding a 2n zygote; AND the union of the other generative nucleus from a pollen grain with the two polar nuclei, yielding 3n endosperm.

Drupe – a fleshy, indehiscent, usually one-seeded fruit with a hard, woody endocarp surrounding the seed. The “stone” (endocarp) often confused for the seed, called a pit or pyrene. A drupelet = small drupe. Example – peach.

Dwarfing rootstock – a rootstock that reduces the potential size and/or vigor of the scion relative to a seedling rootstock.
Effective pollination period – The window of time that pollination can occur and effect fertilization. Can be calculated as the longevity of the embryo-sac minus the time required for pollen germination on the stigma and pollen-tube growth.

Egg nucleus – One of eight nuclei contained within the embryo sac. It fuses with a generative nucleus from a pollen grain, and develops into the zygote and ultimately the embryo within a seed.

Embryo sac – the 8-nucleate cell in the ovule that contains the egg and polar nuclei, and develops into the embryo and endosperm.

Endocarp – the innermost tissue layer of the ovary; often becoming specialized, like the pit of a peach.

Endosperm – The nutritive tissue surrounding the embryo in a seed; created by fusion of one generative nucleus with two polar nuclei during double fertilization. Often absorbed by the cotyledons during seed maturation in dicots.

Endosperm incompatibility – prevention of successful double fertilization caused by the failure of one generative nucleus to unite with the polar nuclei and produce endosperm.

Enology – the study of wine making.

Epigynous – inferior ovary position. The point of attachment of the sepals, petals, and stamens is above the ovary.

Epigynous berry – a berry-like fruit derived from an inferior ovary.

Even pinnate – even number of leaflets in a pinnately compound leaf.

Exocarp – outermost tissue layer of the ovary; often becoming all or part of the fruit skin or peel.

Fecundity – the capacity of a plant for production of great quantities of viable seed.

Fertilization (syn. Syngamy) – The union of a male gamete contained in the pollen grain with the female gamete (egg) in the ovule.

Filament – the stalk of a stamen; organ that holds the anther at its tip.

Flavedo – the exocarp of a citrus fruit. The thin, colored part of the rind, containing the oil glands.

Floral initiation – The first discernable change from a vegetative apex to a reproductive apex; biochemical in nature, not visible under microscope.

Floricane – a flowering branch in brambles; a one-year-old cane on which shoots producing flowers and fruits arise. Floricanes represent the second year of a biennial cane’s life cycle, and die naturally after fruit production.

Generative nucleus – the genetic material of the pollen-bearing plant which goes on to unite with either the egg nucleus or the polar nuclei in the process of double fertilization; each pollen grain contains two generative nuclei.

Germplasm – the genetic variability of a population of organisms. Physically, any plant part containing genetic information that can be used by nurserymen, breeders or genetic engineers to improve or alter a plant species.

Imperfect flower – lacking one of the two sex organs, the androecium or gynoecium.

Incompatibility – with reference to pollination, inability to successfully fertilize an ovule and produce seed. With reference to grafting; a scion/rootstock combination incapable of coexisting. See also delayed incompatibility, endosperm incompatibility, nuclear incompatibility, and pollen tube failure.

Incomplete flower – lacking one or more of the following: calyx (sepals), corolla (petals), androecium, gynoecium.

Indehiscent – not splitting open at maturity.

Inflorescence – a cluster of flowers.

Infructescence – a ripened inflorescence.

Indeterminate – descriptive term applied to inflorescences having the top-most or central flower appearing and maturing last in the blooming sequence.

Lateral - an elongated shoot coming from a main shoot; also used to denote a fruit bearing habit where fruits arise from axillary buds on elongated shoots.Leader – the main axis or central bole of a tree.

Metaxenia – effects of the pollen source on the fruit tissues exclusive of the seeds.

Metric ton – One thousand kilograms, or 2200 lbs.

Mixed bud – a bud possessing both flowers and leaves, as opposed to a simple bud that contains either flowers or leaves.

Monoecious – A plant having separate male and female flowers.

Multiple fruit – fruit produced by the fusion or adherence of two or more ovaries arising from different flowers; a fused inflorescence. Examples – pineapple and mulberry. Sometimes termed a syncarp (syn. syncarpium) if it contains non-ovarian tissues, as it usually does.

Open center – A tree training system where 3-5 main structural limbs (scaffolds) radiate in all directions from a stout trunk 1-3 ft tall. No structural limbs grow in the center of the canopy. Often used with trees having weak apical control and tend to form rounded canopies naturally (e.g., peach, plum, apricot, almond).

Palmate – radiating out from a common point, as with leaflets in palmately compound leaves.

Panicle – a multiply branched, indeterminate inflorescence with 2 or more orders of laterals (mango).

Parthenocarpy (parthenocarpic) – Fruit development in the absence of fertilization and seed production. Vegetative parthenocarpy is the form where pollination need not occur for fruit set, whereas stimulative parthenocarpy is the form where pollination stimulates fruit set, yet fertilization does not occur.

Pedicel – the stalk of a flower.

Peduncle – the stalk supporting the entire inflorescence or a single fruit.

Penetrometer – device for measuring the firmness of fruit flesh.

Pepo – a fleshy fruit from a compound, inferior ovary, with a thick, tough rind. Distinguished from a hesperidium by having parietal placentation instead of axile, and coming from an inferior ovary. Example – watermelon (most Curcurbitaceae).

Perennial – a plant capable of living more than two years.

Perfect flower (syn hermophroditic) – A flower having both male and female parts.

Perigynous – half-inferior ovary position. The point of attachment of the sepals, petals, and stamens surrounds the ovary.

Pest – any organism that reduces yield and/or crop quality.

Petal – a member of the corolla; a floral appendage, often showy.

Petal fall – stage of floral development after anthesis when petals abscise. Often used as visual cue for spray timing.

Pheromone – a chemical insects use for mating and communication.

Phloem – the photosynthate conducting tissue of plants; just beneath the bark and outside of the wood of a stem.

Photosynthate – end products of photosynthesis; sugars mostly.

Phyllotaxy – the arrangement of leaves on a stem. Denoted as a fraction, where the numerator is the number of revolutions around the stem, and the denominator is the number of nodes between two leaves with the same vertical orientation.

Phytotoxic – a chemical that is poisonous to crop plants.

Pilose – covered with soft, long hairs.

Pinnate – with subdivisions arranged oppositely along a main axis in pairs; as in pinnately compound leaves.

Pistil – The female reproductive organ of the flower, composed of the stigma, style, and ovary.

Pistillate – said of a flower or plant containing the gynoecium or pistil(s).

Pit – the endocarp, or stone in a drupe.

Placenta (placentation) – portion of the ovary to which the ovules are attached. Arranged in several ways: axile, basal, free central, or parietal.

Pod – see legume.

Polar nuclei – Two of the eight nuclei contained in a mature embryo sac which form the endosperm of the seed after uniting with one generative nucleus from the pollen.

Pollen tube – An elongated, narrow, tubular structure arising from a germinated pollen grain. It grows through the style and carries the generative nuclei toward the egg sac of the ovule.

Pollen tube failure – Inability of viable pollen to grow at all, or rapidly enough in the style for the generative nuclei to reach the embryo sac and successfully fertilize the egg.

Pollination – transfer of pollen from the anther to the stigma.

Pollinator – an agent of pollen transfer; generally honey bees, or the wind in wind-pollinated species.

Pollinizer (pollenizer) – with reference to cross-pollinated species; a cultivar that functions as a source of compatible pollen.

Polyembryony – two or more embryos arising from a single seed.

Polygamous – having unisexual and bisexual flowers on the same plant.

Polygamodioecious – primarily dioecious, but having some bisexual flowers or flowers of the opposite sex on the same plant.

Polygamomonoecious – primarily monoecious, but having some bisexual flowers.

Pome – a fleshy, indehiscent fruit from an inferior, compound ovary, generally having a cartilaginous endocarp; the fleshy receptacle or hypanthium completely enclosing and fused to the pericarp. Example – apple.

Pome fruits – a group of crops having a pome as a fruit type; members of the Pomoideae subfamily of the Rosaceae (apple, pear, quince, others).

Pomology – the study of fruit culture.

Pomologist – one who studies fruit culture.

Poricidal Capsule – a dry, dehiscent, one- to many-seeded fruit from a single, compound ovary, opening through pores or flaps.

Precocious (n. Precocity) – advanced in development; said of a species with a short period of juvenility. Flowers and bears fruit at a young age.

Primocane – the current season’s shoot that comes from the ground in brambles; vegetative in most cases, except primiocane-fruiting raspberries.

Protandry (Protandrous) – Pollen is shed before the stigma is receptive.

Protogyny (Protogynous, syn Metandry) – The stigma is receptive before pollen is shed.

Schizocarp – A dry, dehiscent fruit from a compound ovary; fruit splits into one-seeded segments at maturity, but carpels do not dehisce to release seeds.

Scion – the above-ground portion of a plant propagated by graftage.

Scion rooting – rooting of the scion portion of the tree as a result of burying the graft union.
Scoring – making knife cuts around the circumference of a stem or branch to impede phloem transport. Similar to girdling, but without removal of a strip of bark.

Seed – A mature ovule. Contains the embryo, endosperm (only remnants in most dicots), and the seed coat(s).

Seedling rootstock – a rootstock propagated by seed.

Self-compatible – capable of successful fertilization and seed production when pollinated with its own pollen.

Self-fruitful – capable of producing a commercial crop of fruit when self pollinated.

Self-incompatibility – incapable of successful fertilization and seed production when pollinated with its own pollen. Not the same as self-sterile; some seed (and thus fruit) will be set in most self-incompatible species when self-pollinated.

Self-pollination – Pollen transfer from the anther to the stigma within the same flower or plant genotype.

Self-sterile – Lacking either pollen or eggs which are viable; cannot produce any viable seed when self-pollinated. Contrast self-incompatible.

Stipules – a pair of generally inconspicuous appendages at the base of the petiole.

Stolon (syn. runner) – a horizontal, creeping stem that roots at the node or tip, producing a new plant.

Stock – abbreviation for rootstock.

Stone fruits – a group of fruit crops belonging to the genus Prunus, which have the fruit type of drupe. (Peach, plum, cherries, apricots).

Strain – a sub-subspecies of a plant; a form. A variant of a cultivar that is nearly identical, not deserving full cultivar status.

Stratification (chilling) – exposure of seed to cool (40 to 50°F) temperatures in the presence of moisture for 30 to 180 days to break seed dormancy and induce uniform germination and seedling development.

Strig – term applied to clusters of fruit in currants and gooseberries.

Style – The part of the pistil between the stigma to the ovary; often slender, elongated.

Sucker (suckering) – shoots arising from the rootstock adventitiously, either from roots or the trunk; undesirable usually, except when occurring on stock plants used for propagation.

Suffrutescent – a shrub that is slightly woody at the base, but mostly composed of herbaceous stems.

Summer pruning – pruning during the growing season.

Superior ovary – hypogynous; see ovary.

Suture – the cleft or line between the base and tip of a stone fruit.

Synchronous protogyny – when all open flowers on the same plant or cultivar have functional female, but not male parts, and later become functionally male. A perfect flower condition that favors outcrossing (Avocado).

Syconium – a fleshy, multiple fruit composed mostly of an inverted, hollow receptacle containing many individual flowers. Access to flowers is provided by a small hole or ostiole (syn. eye) at the fruit tip. Example – Fig, where the true fruits are drupelets (a multiple of drupelets, or a syncarp).

Vegetative propagation – producing a plant asexually, through cuttings, layers, grafting or budding, or tissue culture; NOT by sexual seed. However, apomictic seed can be considered a form of this. Results in plants genetically identical to the parent.

Vine – a plant which is not self-supporting; climbing by means of twining stems or tendrils.